In automobile engines, a fluid or coolant is typically used to carry excess heat from the engine to the radiator. Usually, such coolant is continuously circulated, by an engine-driven pump, through the engine until its temperature exceeds a predetermined level, at which point a portion of the flow is routed through the radiator. The flow is continuously adjusted in an attempt to maintain the temperature of the coolant within a desired range. Often, this is done via a valve that is actuated by a wax motor that is immersed in the flow.
In a known prior art fluid circuit, the radiator and a closure valve are connected in series in the coolant circuit, and a bypass circuit is connected in parallel across the radiator and closure valve. The valve is configured so as to block the flow of coolant through the radiator when the valve is closed. When the valve is closed, the coolant continues to circulate through the engine via the bypass circuit. A disadvantage associated with this configuration is that the bypass flow path remains open at all times such that a substantial portion of the flow of coolant always bypasses the radiator, even if maximum cooling is called for.
Various valves form part of the prior art.
To avoid the problems associated with a permanent bypass flow, these valves provide for the selection between a heat exchanging fluid circuit, which passes through the radiator, or a non-heat exchanging fluid circuit, which short circuits or bypasses the radiator. However, known valves are either relatively expensive, relatively non-robust, or have relatively poor flow characteristics.